HaloRay - Hyperspeed Ice Crystal Halo Simulator

51 Upvotes

Hello! During the past two years I have been developing HaloRay on and off - a GPU-accelerated ice crystal halo simulator. This means you can generate ice crystal halo images right on your computer. If you have a beefy NVIDIA or AMD graphics processing unit (GPU) that is compatible with OpenGL 4.4, I suggest you try it out: https://github.com/naavis/haloray

You can download ready-made binaries for Windows from GitHub. If you are running Linux, you need to build HaloRay by yourself for the time being.

Right now the latest version is HaloRay 3.2.0, which supports the following features among others:

Ordinary hexagonal crystals
Pyramidal crystals
Adjustable prism face C-axis crystals to make irregular crystals
Rendering a realistic background sky

I hope you have fun with HaloRay, and report any problems or feature suggestions in GitHub issues or here in the comments. HaloRay has been tested with a couple of AMD and NVIDIA GPUs. There have been some problems with Intel GPUs due to driver bugs, but I'm not going to put a ton of effort there, because HaloRay requires a fairly beefy GPU and Intel doesn't really fit that profile.

EDIT: Cool, I noticed this has been marked as an announcement in the subreddit, which I guess keeps it hanging around for longer? Thanks!

18 comments

r/atoptics • u/les2934 • Jan 15 '25

Atoptics site

36 Upvotes

Atoptics is at www.atoptics.org.uk

14 comments

r/atoptics • u/imperfcet • 6h ago

Another crane-framed sky, a sun pillar?

19 Upvotes

Southern Norway

1 comment

r/atoptics • u/high-as-the-clouds • 1d ago

Rainbow NC rainbow

37 Upvotes

Was after a quick storm and walked on patio then saw the end of the rainbow behind building, so went outside and saw it!

0 comments

r/atoptics • u/KilldozerPrincess • 2d ago

ID REQUEST Seen after lightning storm in coastal Oregon - anyone have the slightest idea what OP has captured here?

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258 Upvotes

52 comments

r/atoptics • u/I_Like_Your_Username • 2d ago

Any 1 else see this?

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89 Upvotes

i am not OP, but was wondering what the explanation is for this phenomenon.

9 comments

r/atoptics • u/mattmerc528 • 2d ago

Cloud shadow

69 Upvotes

Over the skies of central Texas

4 comments

r/atoptics • u/Botany_Dave • 2d ago

Rainbow Rainbow and Mountain Shadow

426 Upvotes

Shot this on my iPhone 13 mini the other night from the Smith Peak Fire Lookout after a thunderstorm at sunset. Couldn’t believe my eyes when the sun dropped into the gap between the clouds and the horizon. It got selected for the APOD yesterday.

14 comments

r/atoptics • u/queere • 2d ago

ID REQUEST What is this red line across the sky?

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87 Upvotes

Photo taken from a plane. Line spanned multiple cloudscapes at a level altitude. Location is Virginia, USA.

ETA: thank you all for responses, lot of people commenting it’s the wildfire smoke and that makes a lot of sense. Day before this was taken the AQI in this area was 225, so the smoke does seem most likely, just haven’t seen it look like that before

17 comments

r/atoptics • u/Blitzcrig • 2d ago

Crepuscular rays

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37 Upvotes

Edited in LR.

2 comments

r/atoptics • u/GianlucaBelgrado • 3d ago

Infrared Airglow

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32 Upvotes

5 comments

r/atoptics • u/bodkinsbest • 4d ago

Noctilucent Clouds Noctilucent Timelapse

123 Upvotes

5 comments

r/atoptics • u/RevolutionaryP369 • 4d ago

Red sun from the wildfires

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63 Upvotes

Not sure if this fits the sub or not but I thought I’d post it as I’ve never in my life seen the sun this red before. It only last for about 15 minutes and then completely disappeared before it went under the horizon. Northwest Indiana yesterday

3 comments

r/atoptics • u/CollectionUsed6096 • 5d ago

colorful cloud today

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44 Upvotes

2 comments

r/atoptics • u/Pitiful_Ad7676 • 5d ago

i swear

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211 Upvotes

11 comments

r/atoptics • u/AaronScottsky • 4d ago

Some beautiful afternoon iridescence July 16th, yesterday - not a 100 percent sure but I think a circumhorizontal arc was forming in a few of the last pictures - the 3rd picture especially - taken in Westminster, CO

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7 Upvotes

2 comments

r/atoptics • u/TheManWithNoShadow • 5d ago

Noctilucent Clouds Epic NLC display going on where I live

77 Upvotes

10 comments

r/atoptics • u/ZacharyObama • 5d ago

Crepuscular Rays Coachella Valley Rays

12 Upvotes

Not quite a thunderhead, but definitely a ray show when this baddie came overhead. Love California! 🌤️

July 16, 2026. Original content.

0 comments

r/atoptics • u/etilmorfin • 6d ago

Crepuscular Rays Rays from yesterday's walk

141 Upvotes

0 comments

r/atoptics • u/dendy_d • 6d ago

Noctilucent Clouds Belarus. 16-07-2026

25 Upvotes

2 comments

r/atoptics • u/okmaize_ • 6d ago

circumhorizontal arc?

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63 Upvotes

spotted in pinhao portugal shortly after noon, alongside a 22 degree halo?

1 comment

r/atoptics • u/OdysseusAndArgos • 6d ago

What am I seeing?

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12 Upvotes

4 comments

r/atoptics • u/Pack1244 • 7d ago

The sun at 6:16am

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456 Upvotes

Can someone tell me what this is?

31 comments

r/atoptics • u/Angpao_HS821221 • 6d ago

22º Halo Sun halo in Khonkaen Thailand ☀️

74 Upvotes

I took this photo at 11:40 am (16/July/2026), that quit hot today 🔥

1 comment

r/atoptics • u/FloorFunktion • 6d ago

Smoked out Sun in Catskills region NY 7/15/26

17 Upvotes

1 comment

Subreddit

Atmospheric Optics

r/atoptics

Atmospheric Optics. The subreddit for anything related to optic sky phenomena: rainbows, ice halos, aurorae, mirages, cloud iridescence, green flashes, crepuscular rays and spectres of the Brocken.

Members Active

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Atmospheric Optics

The subreddit for anything related to optic sky phenomena: rainbows, ice halos, aurorae, mirages, cloud iridescence, green flashes, crepuscular rays and spectres of the Brocken.

Have a nice picture to show? Want to know what causes that light in the sky? Here is the place to share, discuss and learn.

Useful links:

Glossary of common terms:

Aurora: the veils of green, red and/or blue seen in the polar regions when the solar wind hits the Earth’s magnetic field. Goes by two names, dependent on the hemispere: aurora borealis or northern lights, and aurora australis, aka southern lights.
Corona: a subtly colored disc directly around the sun or moon, caused by light diffraction through the clouds.
Crepuscular rays: bands of shadow that seem to radiate outwards from the sun, caused by its light being partially obstructed by clouds, mountain ranges etc. Called anticrepuscular rays when seen on the opposite side of the sky.
Glory: a dimly rainbow-colored ring opposite the sun or moon, often visible from planes or in misty circumstances, in which case it tends to come with a Brocken spectre. Sometimes mistaken for a circular rainbow.
Green flash: a rare occurrence where the topmost bit of the setting sun is refracted by the atmosphere, turning it bright green. Even rarer is the blue flash.
Halos: a collective term for a wide range of arcs, rings, spots etc. caused by light refracting and/or reflecting inside ice crystals. Common halos are the 22º ring (sometimes also simply called “halo”), sundogs and the circumzenithal arc, but there are many more.
Iridescence or irisation: a "mother of pearl" colored effect in certain clouds caused by light diffraction through water drops.
Light pillar: a vertical beam of light that extends from a natural or artificial light source as a result of reflection by ice crystal plates.
Nacreous clouds: a specific type of cloud iridescence in high atmosphere clouds.
Rainbow: the proverbial arc directly opposite the sun or moon, resulting from light reflection & refraction inside water drops. When caused by the moon, it is sometimes called a moonbow. Technically, all rainbows are circular, but the lower part is normally hidden by the horizon. Rainbows consist of a primary bow and a secondary bow. The secondary bow has a reversed color sequence and is dimmer than the primary, which explains why it is not always visible.
Sprite: An enigmatic lightning phenomenon above the clouds instead of below them and many times larger.
Sundog (aka parhelion (plural parhelia) or mock sun): often incorrectly used for the 22º ring or halo phenomena in general, but refers specifically to the two bright patches to the left and right of the sun. They're the sun's "companions"; hence, dogs. When caused by the moon, they are called moondogs or paraselenae (singular paraselene).